Different firing modes or frequencies occur in the brain and/or other neuronal tissue, for example tonic firing and burst firing (irregular or regular burst firing). Such firing modes can be utilized for normal processing of information, however, alteration of the firing modes, may also lead to pathology.
For example, certain neurological conditions are associated with hyperactivity of the brain and can be traced to a rhythmic burst firing or high frequency tonic firing (e.g., tinnitus, pain, and epilepsy). Other conditions can be associated with an arrhythmic burst firing or a desynchronized form of tonic and burst firing (e.g., movement disorders and hallucinations).
During the past decade, neuromodulation systems have been used to modulate various areas of the brain, spinal cord, or peripheral nerves (see, for example, U.S. Pat. Nos. 6,671,555; 6,690,974). These types of systems utilize tonic forms of electrical stimulation. Recently burst transcranial magnetic stimulation (TMS) at theta frequencies has been developed. Theta burst TMS has been shown to produce an effect on motor and visual cortex by suppressing excitatory circuits after a short application period of only 20-190 s.